Re: [f2fs-dev] [PATCH v2] mkfs.f2fs: check zeros in first 16MB for Android

[Jaegeuk Kim <jaegeuk@kernel.org>]

On 08/10, Ju Hyung Park wrote:
> Hi Jaegeuk,
> 
> Just out of curiosity, what's the point of this?
> 
> I thought flash chips skip erasing blocks if it's already erased to
> preserve P/E cycles as much as possible.
> All Android devices I had(various versions of eMMC and UFS) ran full range
> block-level discards pretty fast too.

Unfortunately, some of them are giving long delays on a bunch of unmap commands
resulting in user janky issue.

> 
> Thanks.
> 
> 2019년 8월 10일 (토) 오전 12:13, Jaegeuk Kim <jaegeuk@kernel.org>님이 작성:
> 
> > We actually don't need to issue trim on entire disk by checking first
> > blocks having zeros.
> >
> > Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
> > ---
> > v2 from v1:
> >  - clean up
> >
> >  mkfs/f2fs_format_utils.c | 53 ++++++++++++++++++++++++++++++++++++++--
> >  1 file changed, 51 insertions(+), 2 deletions(-)
> >
> > diff --git a/mkfs/f2fs_format_utils.c b/mkfs/f2fs_format_utils.c
> > index 8bf128c..f2d55ad 100644
> > --- a/mkfs/f2fs_format_utils.c
> > +++ b/mkfs/f2fs_format_utils.c
> > @@ -25,6 +25,7 @@
> >  #include <stdio.h>
> >  #include <unistd.h>
> >  #include <stdlib.h>
> > +#include <stdbool.h>
> >  #ifndef ANDROID_WINDOWS_HOST
> >  #include <sys/ioctl.h>
> >  #endif
> > @@ -110,13 +111,61 @@ static int trim_device(int i)
> >         return 0;
> >  }
> >
> > +static bool is_wiped_device(int i)
> > +{
> > +#ifdef WITH_ANDROID
> > +       struct device_info *dev = c.devices + i;
> > +       int fd = dev->fd;
> > +       char *buf, *zero_buf;
> > +       bool wiped = true;
> > +       int nblocks = 4096;     /* 16MB size */
> > +       int j;
> > +
> > +       buf = malloc(F2FS_BLKSIZE);
> > +       if (buf == NULL) {
> > +               MSG(1, "\tError: Malloc Failed for buf!!!\n");
> > +               return false;
> > +       }
> > +       zero_buf = calloc(1, F2FS_BLKSIZE);
> > +       if (zero_buf == NULL) {
> > +               MSG(1, "\tError: Calloc Failed for zero buf!!!\n");
> > +               free(buf);
> > +               return false;
> > +       }
> > +
> > +       if (lseek(fd, 0, SEEK_SET) < 0) {
> > +               free(zero_buf);
> > +               free(buf);
> > +               return false;
> > +       }
> > +
> > +       /* check first n blocks */
> > +       for (j = 0; j < nblocks; j++) {
> > +               if (read(fd, buf, F2FS_BLKSIZE) != F2FS_BLKSIZE ||
> > +                               memcmp(buf, zero_buf, F2FS_BLKSIZE)) {
> > +                       wiped = false;
> > +                       break;
> > +               }
> > +       }
> > +       free(zero_buf);
> > +       free(buf);
> > +
> > +       if (wiped)
> > +               MSG(0, "Info: Found all zeros in first %d blocks\n",
> > nblocks);
> > +       return wiped;
> > +#else
> > +       return false;
> > +#endif
> > +}
> > +
> >  int f2fs_trim_devices(void)
> >  {
> >         int i;
> >
> > -       for (i = 0; i < c.ndevs; i++)
> > -               if (trim_device(i))
> > +       for (i = 0; i < c.ndevs; i++) {
> > +               if (!is_wiped_device(i) && trim_device(i))
> >                         return -1;
> > +       }
> >         c.trimmed = 1;
> >         return 0;
> >  }
> > --
> > 2.19.0.605.g01d371f741-goog
> >
> >
> >
> > _______________________________________________
> > Linux-f2fs-devel mailing list
> > Linux-f2fs-devel@lists.sourceforge.net
> > https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel
> >


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